rendering existing categories in view, rails - ruby-on-rails

Question

How do I render a list of existing categories in my views?
My categories table has a :name column.
products view
= f.select :category_name, Category.all.map{|s| [s.name]}
Category.rb
class Category < ActiveRecord::Base
has_many :categoricals
validates :name, uniqueness: { case_sensitive: false }, presence: true
acts_as_tree order: "name"
end
Product.rb
class Product < ActiveRecord::Base
include ActionView::Helpers
include Categorizable
end
UPDATE:
Full product form
= simple_form_for #product, html: { multipart: true } do |f|
= f.input :title, placeholder: "Product Name", required: false, label: false
= f.input :description, placeholder: "Description", required: false, label: false
= f.select :category_name, Category.all.map{|s| s.name}
= f.input :image, label: false
= f.button :submit, class: "button"
UPDATE #2:
products controller
def update
if #product.update(product_params)
redirect_to #product, notice: "Your Product was successfully updated!"
else
render 'edit'
end
end
categorical model
class Categorical < ActiveRecord::Base
belongs_to :category
belongs_to :categorizable, polymorphic: true
validates_presence_of :category, :categorizable
end
categorizable module
module Categorizable
extend ActiveSupport::Concern
included do
has_many :categoricals, as: :categorizable
has_many :categories, through: :categoricals
end
def add_to_category(category)
self.categoricals.create(category: category)
end
def remove_from_category(category)
self.categoricals.find_by(category: category).maybe.destroy
end
module ClassMethods
end
end

Answer 1

I never understand why people don't use collection_select over select:
= f.collection_select :category_id, Category.all, :id, :name
It seems the real problem is due to your relations:
#app/models/category.rb
class Category < ActiveRecord::Base
has_many :products
end
#app/models/product.rb
class Product < ActiveRecord::Base
belongs_to :category #-> requires category_id column in products table
end
This will allow you to reference the :category_id as follows:
= simple_form_for #product, html: { multipart: true } do |f|
= f.input :title, placeholder: "Product Name", required: false, label: false
= f.input :description, placeholder: "Description", required: false, label: false
= f.collection_select :category_id, Category.all, :id, :name
= f.input :image, label: false
= f.button :submit, class: "button"

Answer 2

Try:
= f.select :category_name, Category.all.map{|s| s.name}
In order to make this work, you have to have category_name column present in your products table.